The overall objective of this research proposal is to utilize recombinant DNA technology to identify and isolate the major immunogens of Treponema pallidum, and to test these immunogens as possible effective vaccines against syphilitic infection. The chromosomal DNA of Treponema pallidum (Nichols) will be isolated, purified, and fragmented. Fragments will be cloned via the poly (dG-dC) connector method into the plasmid pBR322. Hybrid plasmid DNA will be used to transform E. coli. Bacterial clones will be selected for in the presence of tetracycline, and resulting clones will be further screened for the presence of T. pallidum DNA inserts by colony hybridization using radioactive nick for the presence of T. pallidum DNA as a probe. A colony band of bacterial clones containing treponemal DNA will establish and clones synthesizing specific T. pallidum immunogens as gene translaton products will be identified by solid-phase radioimmunoassay techniques. Immunogens will be identified, characterized, and isolated from bacterial clones, using analytical and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis in conjunction with immunoprecipitation. Antibody to treponemal immunogens will be produced in rabbits, purified, and used to asses the total number of different antibody specificities to the T. pallidum organism. The ability of antibody to inactivate virulent treponemes will also be examined. Purified treponemal immunogens will be tested for efficacy as potential vaccinogens against syphilitic infection in rabbits.